Mechano-electric clocks



Oct. 18, 1960 E. w. HURD HAL 2,957,116

MECHANO-ELECTRIC CLOCKS Filed June 14, 1957 2 Sheets-Sheet 1 IN VEN TOR W52 0 0 C 'I I ARLQS E. FISCHER SM/THULS UW/J W951i A? TTORNEVS' Oct. 18, 1960 Filed June 14, 1957 E. W. HURD EI'AL I MECHANO-ELECTRIC CLOCKS 2 Sheets-Sheet 2 ELIE-.5

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7 Claims. (Cl. 318-132) This invention relates to mechano-electric clocks and particularly to clocks that derive their operating energy from a zero frequency, or direct current source of electrical energy and which use oscillating mechanical systems to measure the discrete bits of time.

Direct current electric clocks usually use a spring drive for operating the clock and use electromagnetic forces to rewind the spring periodically. A popular use for such clocks is in an automobile. Experience has shown, however, that such clocks are prone to failure for many causes, not the least of which is the failure of the contacts which periodically effect the rewinding of the spring used to drive the clock. The rewinding operation is repeated every three or four minutes. The contacts fail because they interrupt the flow of a large direct current through an inductive load which causes an arc to occur each time the contacts separate. There is suilicient energy in the arc to vaporize small portions of the contacts. Repeated attack on the contacts by the are energy finally causes them to become faulty.

It is an object of our invention to construct an electromechanical clock that does not require the use of electric contacts which interrupt the flow of a large electric current.

It is a further object of our invention to use small direct currents so that sensitive electronic means may be used to control the flow of the electric currents.

Another object of our invention is to create an electromechanical clock whose operating energy is stored in an electric battery as opposed to the usual spring energy storage of clocks superseded by our invention.

Another object of our invention is to create a clock in which the potential energy of the power source for the clock is converted into the kinetic energy of mechanical movement in very small amounts with each oscillation of the mechanical oscillating device controlling the time measuring function of the clock.

A further object of our invention is to produce a clock drive characterized by a long life and high reliability, with infrequent need for battery replacement, if battery operated.

An additional object of our invention is to produce a clock drive whose parts are capable of mass production and sub-assemblies of which may be automatically assembled into a finished article of commerce.

These and other objects will become apparent as we describe our invention. Though the description relates to a particular embodiment of our invention, other means of using the basic philosophy of our invention exist that will be recognized by those skilled in the mechanical andelectrical sciences.

. .In the drawings:

Fig. 1 is a schematic diagram of the various electrical connections, and components in a preferred embodiment of the electro-mechanical oscillator, I

Fig. .2 is a time-function diagram of the electro-i in parallel with coil 17. This resistance serves as a means 0 grees (maximum clockwise excursion). The zero angue lar position shall be defined as the position shown for the;

mechanicalfsequence of events in the clock, and

ice

Fig. 3 is a drawing of our electro-mechanical oscillator connected to a clock mechanism.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring now to the circuit of Fig. 1, a PNP transistor is shown at 10, having the terminals 11, 12, and 13 connected to the emitter, base and collector terminals of said transistor 10. Control coil 14 is connected between base terminal 12 and emitter terminal 11 by means of conductors 15, 16, 22 and resistor 30. Motor coil 17, magnetically coupled with coil 14, is connected to col lector terminal 13 by means of conductor 18 and to terminal 33 with conductor 20. Emitter terminal 11 is connected to terminal 34 by means of conductor 22. The terminals 33 and 34 serve as connection points to a regulated source of electrical energy with the polarity as indi cated (terminal 33 negative, and terminal 34 positive). The voltage regulating bridge comprised of resistances 28, 29 and 30 and the voltage compensating resistors 31, 32 is shown connected in a manner well known in the art to produce a relatively constant voltage between the terminals 33 and 34 and similarly between terminals 29:: and 34 despite wide fluctuation in the voltage applied to terminals 19 and 21. Resistance 27 is shown connected for reducing the tendency of the circuit to oscillate electrically.

The wheel 23, pivotally mounted on the balance staff or axis 24, comprises a mechanical oscillating element with hair spring 23a.

A small magnet 25 is afiixed to the periphery of the wheel 23. The wheel 23 and associated parts are mounted physically and magnetically adjacent to the coils 14 and 17. The coils 14 and 17 are usually concentrically wound on a magnetizable core, shown schematically at 26.

In order to understand clearly the operation of the base electrode 12 is negative with respect to the emitter electrode 11. If the base electrode 12 is positive with respect to the emitter electrode 11, negligible current flow occurs through the transistor between emitter electrode 11 and collector electrode 13.

To aid in describing the operation of the invention the function-time chart of Fig. 2. will be used. The functiontime chart of Fig. 2 has for its abscissa the angular position of the oscillating balance wheel 23. position is defined as the angle P existing between a line 34 drawn through the center of the balance wheel axis 24 and the magnet 25, and another line 35 drawn parallel to the magnetic core 26 and intersecting the balance wheel axis 24 and theline 34. The angular excursion P of the balance wheel 23 during sustained operation of our elec-' tro-mechanical oscillator is approximately constant. For.

the purpose of simplifying the present description the maximum value of -P shall be taken as +180 degrees (maximum counterclockwise excursion) and l demagnet g 1 with lines 34 and 35 coincident" The angular Since the purpose of the invention is to produce a force pulse at precisely the correct moment to sustain the mechanical oscillation of the balance wheel, the description of the operating principles of the device shall be given in a chronological order corresponding to the periodic chronology of theoscillating balance wheel 23. The starting time shall'be taken at the instant the balance wheel 23 has come to rest at the extreme of its counterclockwise excursion. The time corresponding to this instant is shown at 36 on the time-function chart of Fig. 2. At this instant, the voltage V which represents the generated voltage in control coil 14 has the value E which is the potential drop across resistor 30 caused by the .fiow of current through resistor 30; the currents I and 1 through the control or emitter-base circuit and the motor or emitter-collector circuit, respectively, are negligibly small and the magnetic torque T is essentially zero. The balance wheel 23 is motionless. .An instant later from the time corresponding to point 36 on the time abscissa, the balance wheel 23 is accelerating in a clockwise direction and the balance spring torque, though still clockwise, is reducing toward zero. All other functions remain in substantially the same condition as for time 36.

At approximately time 37, V 1 I have still substantially the same values as for time 36 but T which is the magnetic torque exerted on the balance wheel 23 by the attractive forces existing between permanent magnet 25 and magnetic core 26, has now started to increase producing a clockwise torque 46 on the balance wheel 23.

Under the influence of the clockwise magnetic torque, T as indicated at 46, the angular speed of the balance wheel 23 is increased as indicated at 38. As time progresses, the magnet 25 causes a voltage to be generated in the coil 14 as charted at 39 V Since the generated voltage is arranged to produce a positive voltage pulse at the base electrode '12 of the transistor 10 with respect to the emitter 11, no change in transistor collector circuit current 1 values takes place. In addition, the magnet 25 is being attracted to the magnetic core 26 as plotted at 39a, which attraction produces a magnetic torque 46 as plotted.

At the instant the angular position P reaches zero, i.e., the magnet axis 25 is co-linear with the magnetic core 26 axis, the generated voltage in coil 14, plotted in Fig. 2 as V reverses in polarity. The reverse polarity of the generated voltage may be verified experimentally and conforms with the mathematical statement of the voltage generation in a coil subject to a changing magnetic field. Thus the voltage generated by the coil 14 under the influence of the magnetic field produced by magnet 25 may be stated:

e: dt

in which e is the instantaneous value of generated voltage appearing across coil 14, K is a constant dependent on the geometry of the coil, number of turns, coupling factors and similar constant parameters, and

is the time rate of change of the number of magnetic lines of force threading the coil. Numerical values of are positive when the field intensity is increasing, negative when the field intensity is decreasing and zero when the field insten'sity is neither increasing nor decreasing. As

increases .in a negative direction, it reach a value such that e--IE =O and f nally e will exceed E so that a negative pulse of voltage is applied to the base electrode 12 as referred to the emitter electrode 11. A current 1 now starts to flow as indicated at 4il which, in accordance with the principles of transistor operation previously explained, permits a current I indicated at 41 to flow through motor coil 17. The current I flowing in coil 17 induces a voltage in coil 14 of such polarity as to create a still greater negative voltage applied to the base electrode 12. This regenerative action continues until the inherent current limiting mechanisms of the transistor 10 or associated electrical circuitry resist any further increase in I at which time the voltage induced in coil 14 by the rising value of I reduces to zero. The value of 1 starts to reduce and induces a positive pulse 42 of voltage in coil 14 which positive pulse hastens the decline 43 of I toward zero. The pulse 41 of current l during its existence flows through coil 17 and produced a magnetomotive force in magnetic core 26 opposing the magnetomotive force arising from the proximity of magnet 25 to magnetic core 26. A repulsive magnetic force as shown at 44 is therefore produced which produces a clock-wise torque pulse 45 on the balance wheel 23, thus imparting a small bit of mechanical energy to the balance wheel for overcoming inherent friction losses in the mechanical system or for providing energy needed to actuate the necessary gears, escapements, and other mechanical devices common to clocks and similar mechanisms.

The plot of magnetic force shown in Fig. 2 reveals a repulsive force 44 caused by the current pulse 41 I flowing through coil 17. It is possible that the magnitude of pulse 41 will diminish for various reasons such as power source deterioration, or shift in transistor characteristics. Such diminution could result in either the reduction or elimination of the magnetic torque pulse 45. We have found, however, that electro-mechanical oscillation of the system will still be maintained inasmuch as the attractive forces represented by magnetic torque pulses 46 are capable of sustaining the mechanical oscillation.

The magnetic torque pulse 45 now having reduced to zero by time 37a, the balance spring torque is now the predominant influence on further rotation of the balance wheel, and, since the balance spring is exerting a counterclockwise torque 47, the balance wheel angular rate starts to reduce toward zero 48. Finally, the kinetic energy of the balance wheel is converted to potential energy in the balance wheel spring and the balance wheel is stopped as shown at 49. The counter-clockwise torque being exerted on the balance wheel 23 by the balance wheel spring 23a is immediately effective in reversing the balance wheel 23 and it begins to rotate clockwise as indicated at 50.

As in the previous half cycle of electro-mechanical oscillation, corresponding to a shift from +180 degrees P angular position 36 to l80 degrees P angular position 51, the magnetic and electro-magnetic forces produce a torque applied to the balance wheel 23 so as to replenish the friction losses and mechanical effort performed by the balance wheel and the usual mechanical contrivances co-operative with it in a clock mechanism.

Thus it can be seen that the invention consists in part of an electro-mechanical oscillating system in which the basic oscillating element is the familiar balance wheel and spring, and that the mechanical losses from such a system are replenished by a torque pulse magnetically delivered to the balance wheel, which torque pulse is created by an electric oscillator restrained from displaying any tendency to oscillate except at those times propitious for the maintenance of mechanical oscillation of the balance wheel. We have determined experimentally that the electric oscillations in the circuit of the transistor and associated coils is undesirable because it is difiicult to adjust the electric oscillations of the electric circuit and the mechanical oscillations of the balance wheel to J in this regard were eliminated by inhibiting the ability of the electric oscillator to oscillate except in single pulses by applying a bias voltage E between the base electrode 12 and the emitter electrode 11 and by resistively loading the coil 17 with resistor 27. The bias voltage E will vary for different transistors. For the 2N155 transistor, a bias voltage E equal to 0.3 volt is capable of inhibiting oscillation for the operating conditions normally encountered in automotive clock service.

Occasionally a second pulse of current I 52 occurs after the primary pulse. The second pulse may be as large as the first pulse or considerably smaller. We have determined experimentally that the second pulse is caused by damped oscillation in the coil 14 which may cause a second pulse of voltage 54 to overcome the transistor bias 55 and thus to initiate the regenerative action of the circuit. A slight increase in the bias E will prevent such spurious pulses 52.

The sustained oscillating motion of the balance wheel 23 may be transformed into a uni-directional rotating motion by a number of different devices. We have chosen for the present construction of our device the mechanism shown schematically in Fig. 3. The bal ance wheel 23 oscillates on balance staif 24 under the influence of balance spring 23a. The frictional losses of the balance wheel system and the mechanical energy necessary to operate the clock are delivered to the balance wheel using the magnet 25 aflixed to the balance wheel 23' and the magnetic core 26 and coil structure indicated at 14a and 17a.

Oscillating motion of the balance wheel 23 causes balance stall 24 to oscillate which in turn causes pin-disc 56 to oscillate to the same angular extent. Pin arm 57 is co-operatively engaged with pin 57a mounted on pindisc 56. Pin-arm 57 is rotatably mounted on pin-arm shaft 57b. Shaft 57b is mounted on pad 570 and accurately positioned by hearing guide 57d. Co-operative engagement of pin 57a with pin yoke 57e causes indexing head 57f to reciprocate as shown by arrow 57g. Slant teeth 58 by their reciprocation and mechanical cooperation with cogs 59 cause pin wheel 66 to rotate uni-directionally as shown by arrow 61. Pin wheel rotation causes shaft 62 to rotate and thus operate the clock mechanism shown at 63.

Having thus explained our invention, we claim:

1. In combination, a mechanical oscillating device having a permanent magnet whose magnetic field dimensions are small relative to the total mechanical excursion of said oscillating device so that the magnetic reaction of the permanent magnet with a cooperating motor coil is limited to a small time fracion of the total mechanical excursion of the oscillating device, and a transistor circuit for producing a magnetic force pulse on the permanent magnet at the correct moment to sustain mechanical oscillation of the device comprising a transistor having an emitter electrode, a collector electrode and a base elec-' trode, an emitter-base circuit including a control coil, an emitter-collector circuit including a motor coil, said control and motor coils being wound on a common magnetic core of such size as to be magnetically effective on said permanent magnet for a small time fraction of the total period of said oscillating device and mounted in juxtaposition to said permanent magnet so that as the permanent magnet approaches said core a voltage is generated in the emitter-base circuit to prevent current flow through the emitter-collector circuit and initially as the permanent magnet begins to recede from said core the induced voltage in the emitter-base circuit reverses in polarity allowing current flow through said emitter-collector circuit for producing said magnetic force pulse, and a source of electric supply to said emitter-base and emitter-collector circuits.

2. In combination, a mechanical oscillating device having a permanent magnet whose magnetic field dimensions are small relative to the total mechanical excursion of said oscillating device so that the magnetic reaction of the permanent magnet with a cooperating motor coil is limited to a small time fraction of the total mechanical excursion of the oscillating device, and a transistor circuit for producing a magnetic force pulse on the permanent magnet at the correct moment to sustain mechanical oscillation of the device comprising a transistor having an emitter electrode, a collector electrode and a base electrode, an emitter-base circuit including a control coil, an emitter-collector circuit including a motor coil, said control and motor coils being wound on a common magnetic core of such size as to be magnetically effective on said permanent magnet for a small time fraction of the total period of said oscillating device and mounted in juxtaposition to said permanent magnet so that as the permanent magnet approaches said core a voltage is generated in the emitter-base circuit to prevent current flow through the emitter-collector circuit and initially as the permanent magnet begins to recede from said core the induced voltage in the emitter-base circuit reverses in polarity allowing current flow through said emitter-collector circuit for producing said magnetic force pulse, a source of electric supply to said emitter-base and emitter-collector circuits, and a voltage regulator for maintaining a relatively constant voltage to the emitterbase and emitter-collector circuits irrespective of fluctuations in the voltage from said source.

3. In combination, a mechanical oscillating device having a permanent magnet whose magnetic field dimensions are small relative to the total mechanical excursion of said oscillating device so that the magnetic reaction of the permanent magnet with a cooperating motor coil is limited to a small time fraction of the total mechanical excursion of the oscillating device, and a transistor circuit for producing a magnetic force pulse on the permanent magnet at the correct moment to sustain mechanical oscillation of the device comprising a transistor having an emitter electrode, a collector electrode and a base electrode, an emitter-base circuit including a control coil, an emitter-collector circuit including a motor coil, said control and motor coils being wound on a common magnetic core of such size as to be magnetically effective on said permanent magnet for a small time fraction of the total period of said oscillating device and mounted in juxtaposition to said permanent magnet so that as the permanent magnet approaches said core a voltage is generated in the emitter-base circuit to prevent current flow through the emitter-collector circuit and initially as the permanent magnet begins to recede from said core the induced voltage in the emitter-base circuit reverses in polarity allowing current flow through said emittercollector circuit for producing said magnetic force pulse, a resistance connected in parallel with said motor coil for reducing the tendency of the emitter-collector circuit to oscillate electrically, and a source of electric supply to,

said emitter-base and emitter-collector circuits.

4. In combination, a mechanical oscillating device having a permanent magnet whose magnetic field dimensions are small relative to the total mechanical excursion of said oscillating device so that the magnetic reaction of the permanent magnet with a cooperating motor coil is limited to a small time fraction of the total mechanical excursion of the oscillating device, and a transistor circuit for producing a magnetic force pulse on the permanent magnet at the correct moment to sustain mechanical oscillation of the device comprising a transistor having an emitter electrode, a collector electrode and a base electrode, an emitter-base circuit including a control coil, an emitter-collector circuit including a motor coil, said control and motor coils being wound on a common magnetic core of such size as to be magnetically effective on said permanent magnet for a small time fraction of the total period of said oscillating device and mounted in juxtaposition to said permanent magnet so that as the permanent magnet approaches said core a voltage is generated in the emitter-base circuit to prevent current flow through the emitter-collector circuit and initially as the permanent magnet begins to recede from said core the induced voltage in the emitter-base circuit reverses. in polarity allowing current flow through said emittercollector circuit for producing said magnetic force pulse, a

resistance connected in parallel with said motor coil for reducing the tendency of the emitter-collector circuit to oscillate electrically, a source of electric supply to said emitter-base and emitter-collector circuits, and a voltage regulator for maintaining a relatively constant voltage to the emitter-base and emitter-collector circuits irrespective of fluctuations in the voltage from said source.

5. In combination, a mechanical oscillating device having a permanent magnet whose magnetic field dimensions are small relative to the total mechanical excursion of said oscillating device so that the magnetic reaction of the permanent magnet with a cooperating motor coil is limited to a small time fraction of the total mechanical excursion of the oscillating device, and a transistor circuit for producing a magnetic force pulse on the permanent magnet at the correct moment to sustain mechanical oscillation of the device comprising a transistor having an emitter electrode, a collector electrode and a base electrode, an emitter-base circuit including a control core,

an emitter-collector circuit including a motor coil, said control and motor coils being wound on a common magnetic core of such size as to be magnetically effective on said permanent magnet for a small time fraction of the total period of said oscillating device and mounted in juxtaposition to said permanent magnet so that as the permanent magnet approaches said core a voltage is generated in the emitter-base circuit to prevent current flow through the emitter-collector circuit and initially as the permanent magnet begins to recede from said core the induced voltage in the emitter-base circuit reverses in polarity allowing current flow through said emitter-collector circuit for producing said magnetic force pulse, a resistance across the emitter-base circuit to eiiect a voltage bias between the emitter-electrode and the base electrode for inhibiting the electric oscillator from oscillating except in single pulses, and a source of electric supply to said emitter-base and emitter-collector circuits.

6. In combination, a mechanical oscillating device having a permanent magnet whose magnetic field dimensions are small relative to the total mechanical excursion of said oscillating device so that the magnetic reaction of the permanent magnet with a cooperating motor coil is limited to a small time fraction of the total mechanical excursion of the oscillating device, and a transistor circuit for producing a magnetic force pulse on the permanent magnet at the correct moment to sustain mechanical oscillation of the device comprising a transistor having an emitter electrode, a collector electrode and a base electrode, an emitter-base circuit including a control coil, an emitter-collector circuit including a motor coil, said control and motor coils being Wound on a common magnetic core of such size as to be magnetically efiective on said permanent magnet for a small time fraction of the total period of said Oscillating device and mounted in juxtaposition to said permanent magnet so that as the permanent magnet approaches said core a voltage is generated in the emitter-base circuit to prevent current flow through the emitter-collector circuit and initially as the permanent magnet begins to recede from said core the induced voltage in the emitter-base circuit reverses in polarity allowing current flow through said emittercollector circuit for producing said magnetic force pulse, a resistance connected in parallel with said motor coil and a resistance connected across the emitter-base cir cuit between the emitter-electrode and base-electrode for reducing the tendency of the emitter-collector circuit to oscillate and for inhibiting the electric oscillator from oscillating except in single pulses.

7. In combination, a mechanical oscillating device having a permanent magnet whose magnetic field dimension are small relative to the total mechanical excursion of said oscillating device so that the magnetic reaction of the permanent magnet With a cooperating motor coil is limited to a small time fraction of the total mechanical excursion of the oscillating device, and a transistor circuit for producing a magnetic force pulse on the permanent magnet at the correct moment to sustain mechanical oscillation of the device comprising a transistor having an emitter electrode, a collector electrode and a base electrode, an emitter-base circuit including a control coil, an emitter-collector circuit including a motor coil, said control and motor coils being wound on a common magnetic core of such size as to be magnetically efiective on said permanent magnet for a small time fraction of the total period of said oscillating device and mounted in juxtaposition to said permanent magnet so that as the permanent magnet approaches said core a voltage is generated in the emitter-base circuit to prevent current flow through the emitter-collector circuit and initially as the permanent magnet begins to recede from said core the induced voltage in the emitter-base circuit reverses in polarity allowing current flow through said emitter-collector circuit for producing said magnetic force pulse, a resistance connected in parallel with said motor coil and a resistance connected across the emitter-base circuit between the emitter-electrode and base-electrode for reducing the tendency of the emitter-collector circuit to oscillate and for inhibiting the electric oscillator from oscillating except in single pulses, a source of electric supply to said emitter-base and emitter-collector circuits, and a voltage regulator for maintaining a relatively constant voltage to the emitter-base and emitter-collector circuits irrespective of fluctuations in the voltage from said source.

References Cited in the file of this patent UNITED STATES PATENTS 2,472,249 De Giers et al. June 7, 1949- 2,652,460 Wallace Sept. 15, 1953 2,751,550 Chase June 19, 1956 2,831,114 Van Overbeek Apr. 15, 1958 2,843,742 Cluwen July 15, 1958 2,877,399 Shaull Mar. 10, 1959 FOREIGN PATENTS 746,465 Great Britain Mar. 14, 1956 761,609 Great Britain Nov. 14, 1956 789,483 France Aug. 19, 1935 923,788 France Feb. 24, 1947 1,090,564 France Oct. 20, 1954 M an. a. a 

